1. Field of Invention
The present invention relates to a general-purpose V-type 2-cylinder engine to be used mainly in an industrial machine, an agricultural machine or the like and, more particularly, to a V-type 2-cylinder engine having a fuel injection device in a V-space between the cylinders.
2. Description of Related Art
In industrial engines to be used in agricultural machines, small-sized power generators or the like, a carburetor is generally employed as a fuel feeding device in an intake system. In considering the response of the engine at acceleration/deceleration, the countermeasures against exhaust emissions of recent years and the equal distribution of air-fuel mixtures, however, it is thought that a fuel injection device (especially, an electronic control type fuel injection system) for injecting gasoline directly into the intake pipe is advantageous over the carburetor. From this background, the fuel injection device is adopted in a V-type 2-cylinder engine, which is advantageous for its compact size.
In a general-purpose V-type 2-cylinder engine provided with the fuel injection device, one injection valve for distributing the air-fuel mixture to the two cylinders is adopted, which saves space. In the 2-cylinder engine, however, the intake timings are heterogeneous for the individual cylinders. By using one injection valve, therefore, the mixtures to be distributed to the individual cylinders are different in their flows and air/fuel ratios, and further, the passages from the injection valve to the intake ports are elongated to make the fuel atomizations poor.
In order to make equal the air-fuel mixture distributions to the individual cylinders, each cylinder is provided with one fuel injection valve (as referred to in Japan Laid Open Patent No. 2000-145596). With this arrangement, it is effective, to an extent, to distribute the air-fuel mixtures equally to the individual cylinders. However, a large arrangement space is required for arranging components such as the two fuel injection valves, fuel distribution pipes for distributing the fuels to those two fuel injection valves, and a fuel pressure adjustor (or a fuel pressure regulator) necessary for adjusting the pressures of the fuels to be distributed and fed to the two fuel injection valves. Moreover, complex fuel passages or piping constructions are required, which provides an inferior appearance. As a result, the degree of freedom for structures and designs is lowered in industrial machines, agricultural machines or the like, on which the V-type 2-cylinder engine having the fuel injection device is mounted. Moreover, the increase in the number of parts and the assembling time for mounting the parts raises manufacturing cost.
Accordingly, it is an object of the present invention to provide a V-type 2-cylinder engine having a fuel injection device capable of distributing air-fuel mixtures equally to each cylinder, having a compact arrangement, having an improved assembling performance, and reducing manufacturing cost.
According to the first aspect of the present invention, a V-type 2-cylinder engine comprises a V space between cylinders, a fuel injector arranged in each cylinder in the V space, a fuel pressure adjustor disposed in the V-space for adjusting a pressure of fuel to be fed to the fuel injectors, a throttle body forming a section of an intake passage and having a throttle valve, and an injection fuel introduction portion of a fuel passage formed in the throttle body. In this aspect, the fuel pressure adjustor is disposed in the injection fuel introduction portion of the fuel passage.
According to the V-type 2-cylinder engine, the main components of the fuel injection device, i.e., the two fuel injectors and the fuel pressure adjustor, are disposed together in the V-space, so that the V-space can be effectively exploited as an accommodation space. Moreover, the section of the intake passage and the injection fuel introduction portion of the fuel passage are formed in the throttle body so that a fuel pipe for supplying fuel to the fuel introduction portion can be easily connected to the fuel introduction portion and so that the engine can be changed from the fuel injection type into a carburetor type by replacing the throttle body with a carburetor. Moreover, the fuel pressure adjustor to be disposed in the V-space is mounted in the injection fuel introduction portion of the fuel passage, that is, in the throttle body so that the entire fuel injection device containing the throttle body is compactly confined in the V-space to improve the appearance. Moreover, each cylinder is provided with one fuel injector so that the injector can be arranged close to the intake portion of a corresponding cylinder. In the case where fuel is injected from the fuel injector to the intake port, therefore, less fuel sticks to the wall face of the intake portion so that atomization of the fuel is improved.
Preferably, the fuel pressure adjustor is disposed between the fuel injectors provided in each cylinder.
Thus, the arrangement of the two fuel injectors and the fuel pressure adjustor is well balanced making the fuel injection device more compact. Moreover, the fuel pressure adjustor can be arranged at an equal spacing from the two fuel injectors so that the fuel pressure adjustment can be made equally and highly accurately for both of the fuel injectors.
Preferably, the injection fuel introduction portion of the fuel passage is formed integrally with the throttle body. Thus, the introduction portion of the fuel passage neither needs to be made of a new separate member, nor requires bolts or the like for mounting the introduction portion. As a result, the number of parts can be reduced while improving mountability and assembling performance.
Preferably, an intake manifold having the fuel injector is disposed between the throttle body and the intake port of the cylinder, and a fuel introduction pipe for feeding fuel from the introduction portion of the fuel passage to the fuel injector is provided, wherein the fuel introduction pipe is inserted and supported between the throttle body and the intake manifold.
Thus, the fuel introduction pipe for feeding the fuel to the fuel injector can be easily mounted without requiring bolts, or the like, by inserting the fuel introduction pipe between the throttle body and the intake manifold. Thus, not only are the number of parts reduced, but also the mountability and the assembling performance are improved.
Preferably, the fuel injector is inserted and supported between the fuel introduction pipe and the intake manifold. Thus, the fuel injector can be easily mounted by inserting it between the throttle body and the intake manifold so that mounting members can be eliminated, which also improves the mountability and assembling performance.
Preferably, the fuel pressure adjustor is disposed on one side of the fuel injectors in a longitudinal direction along the rotational axis of the engine, whereas a pressure sensor for detecting the pressure in the intake passages is arranged on the other side. Thus, the fuel pressure adjustor and the pressure sensor can be disposed close to other components easily and the arrangement is well balanced to make the fuel injection device compact.
Preferably, an intake introducing intake duct member is connected to the downstream side of an air cleaner, and the throttle body is connected to the intake introducing intake duct member. The intake manifold having the fuel injectors is disposed between the throttle body and the intake ports of the cylinders. Thus, a general carburetor type V-type 2-cylinder engine can be easily changed to a fuel injection type V-type 2-cylinder engine by replacing a carburetor of the engine and a manifold for the carburetor with the throttle body and intake manifold. According to the need or driving conditions, therefore, the specifications of the engine can be promptly changed from the carburetor type engine to the fuel injection device type engine of the invention.